The United States has new legal limits on electronic surveillance, both in one specific way and — more important — in prevailing judicial theory. This falls far short of the protections we ultimately need, but it’s a welcome development even so.

The recent Supreme Court case Carpenter v. United States is a big deal. Let me start by saying:

Most fundamentally, the Carpenter decision was based on and implicitly reaffirms the Katz test.* This is good.

The Carpenter decision undermines the third-party doctrine.** This is great. Strict adherence to the third-party doctrine would eventually have given the government unlimited rights of Orwellian surveillance.

The Carpenter decision suggests the Court has adopted an equilibrium-adjustment approach to Fourth Amendment jurisprudence.

The “equilibrium” being maintained here is the balance between governmental rights to intrude on privacy and citizens’ rights not to be intruded on.

e., equilibrium-adjustment is a commitment to maintaining approximately the same level of liberty (with respect to surveillance) we’ve had all along.

I got the equilibrium-adjustment point from Eugene Volokh’s excellent overview of the Carpenter decision.

*The Katz test basically says that that an individual’s right to privacy is whatever society regards as a reasonable expectation of privacy at that time.

**The third-party doctrine basically says that any information of yours given voluntarily to a third party isn’t private. This includes transactional information such as purchases or telephone call detail records (CDRs)

Key specifics include:

The actual issue in Carpenter is whether the government needs a warrant to access cell phone location data that allows a cell phone user’s movements to be quite accurately tracked. The decision on that issue was Yes.

This was a 5-4 decision. Chief Justice Roberts and the four liberal justices voted for it. Swing voter Justice Kennedy and the other three conservative justices voted against it.

The majority was united. Justice Roberts wrote the decision and there were no concurrences.

The dissents were not united, but did generally focus on two kinds of arguments:

Reliance on the third-party doctrine, commonly expressed as reliance on the Smith and Miller precedents.

Disagreement with the Katz test.

Also very relevant was the 2012 case requiring warrants for GPS tracking, United States v Jones. But discussion of the Jones decision is confusing, because while some justices at the time addressed the issue of general electronic tracking of a person’s movements, others focused narrowly on the physical action of installing the GPS device.

Unfortunately, all the good news in Carpenter notwithstanding, the decision doesn’t come close to accomplishing as much as we need. I stand by my oft-repeated observations:

Massive surveillance is inevitable.

Unless the uses of the resulting information are VERY limited, freedoms will be chilled into oblivion.

Justice Roberts correctly wrote in the Carpenter decision:

Mapping a cell phone’s location … provides an intimate window into a person’s life, revealing not only his particular movements, but through them his “familial, political, professional, religious, and sexual associations.”

Justice Kennedy however rejoindered:

What persons purchase and to whom they talk might disclose how much money they make; the political and religious organizations to which they donate; whether they have visited a psychiatrist, plastic surgeon, abortion clinic, or AIDS treatment center; whether they go to gay bars or straight ones; and who are their closest friends and family members.

His point, also correct, was that the data that police are allowed to get without warrants is even more privacy-violating than the data Carpenter keeps away from them. And so, as good as the Carpenter decision apparently is, privacy invasion and surveillance are still among the gravest threats to liberty that we face.

Related links

My January post on the chaotic politics of privacy is relevant both to the content of the Carpenter decision and to the fact that the decision-makers did not split perfectly along traditional partisan lines.

My 2013 series on privacy theory suggests that gaps in judicial reasoning could be filled by referencing the problem of chilling effects.